This invention relates to bottom operable railway tank car valves, and to the removal of damaged portions of the bottom operable valve while the closure portion of the valve remains closed and lading is retained in the tank.
The bottom operable tank car valve in U.S. Pat. No. 3,981,481 includes a valve closure portion which in closed position closes the opening in the bottom of the tank, preventing lading discharge; and an operating assembly for moving the closure portion relative to the tank bottom opening for loading and/or unloading lading. The operating assembly includes a first threaded operator which is attached to the closure portion with removable fasteners. The first operator depends from the valve closure portion and engages a second, rotatable threaded operator. The second threaded operator remains vertically fixed by a retainer as it is rotated and engages the first threaded operator and moves it and the closure portion vertically between opened and closed position. The retainer has spaced ribs extending radially between a tank bottom flange portion and the second operator to maintain the valve closure seated when the valve closure is in closed position.
Railway tank cars occasionally derail and in some instances the tank becomes dislodged from the car truck. If the tank has a bottom operable lading loading and/or unloading valve, such as the one disclosed in said U.S. Pat. No. 3,981,481, severe impacts to the valve assembly may occur during and/or after such derailment. Such impacts may damage or render inoperative some or all of the operating mechanism used to unload the lading from the tank.